/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Selection/GeometrySelector.h
Selector implementations should ideally have a strategy to lazy-construct any large data structures (eg mesh AABBTrees, etc). Again this is to avoid excessive overhead when the user (for example) selects a large object but has no intention of doing element-level selection.
class IGeometrySelector
FOnGeometryModi...
OnGeometryModifed